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<p class="level0"><a name="NAME"></a><h2 class="nroffsh">NAME</h2>
<p class="level0">CURLOPT_SEEKFUNCTION - user callback for seeking in input stream <a name="SYNOPSIS"></a><h2 class="nroffsh">SYNOPSIS</h2>
<p class="level0"><pre>
<p class="level0">#include &lt;curl/curl.h&gt;
 <p class="level0">/* These are the return codes for the seek callbacks */
 #define CURL_SEEKFUNC_OK       0
 #define CURL_SEEKFUNC_FAIL     1 /* fail the entire transfer */
 #define CURL_SEEKFUNC_CANTSEEK 2 /* tell libcurl seeking can't be done, so
 &nbsp;                                   libcurl might try other means instead */
 <p class="level0">int seek_callback(void *userp, curl_off_t offset, int origin);
 <p class="level0">CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SEEKFUNCTION, seek_callback);
 </pre>
<a name="DESCRIPTION"></a><h2 class="nroffsh">DESCRIPTION</h2>
<p class="level0">Pass a pointer to your callback function, which should match the prototype shown above. 
<p class="level0">This function gets called by libcurl to seek to a certain position in the input stream and can be used to fast forward a file in a resumed upload (instead of reading all uploaded bytes with the normal read function/callback). It is also called to rewind a stream when doing a HTTP PUT or POST with a multi-pass authentication method. The function shall work like fseek(3) or lseek(3) and it gets SEEK_SET, SEEK_CUR or SEEK_END as argument for <span Class="emphasis">origin</span>, although libcurl currently only passes SEEK_SET. 
<p class="level0"><span Class="emphasis">userp</span> is the pointer you set with <a Class="emphasis" href="./CURLOPT_SEEKDATA.html">CURLOPT_SEEKDATA</a>. 
<p class="level0">The callback function must return <span Class="emphasis">CURL_SEEKFUNC_OK</span> on success, <span Class="emphasis">CURL_SEEKFUNC_FAIL</span> to cause the upload operation to fail or <span Class="emphasis">CURL_SEEKFUNC_CANTSEEK</span> to indicate that while the seek failed, libcurl is free to work around the problem if possible. The latter can sometimes be done by instead reading from the input or similar. 
<p class="level0">If you forward the input arguments directly to fseek(3) or lseek(3), note that the data type for <span Class="emphasis">offset</span> is not the same as defined for curl_off_t on many systems! <a name="DEFAULT"></a><h2 class="nroffsh">DEFAULT</h2>
<p class="level0">By default, this is NULL and unused. <a name="PROTOCOLS"></a><h2 class="nroffsh">PROTOCOLS</h2>
<p class="level0">HTTP, FTP, SFTP <a name="EXAMPLE"></a><h2 class="nroffsh">EXAMPLE</h2>
<p class="level0">TODO <a name="AVAILABILITY"></a><h2 class="nroffsh">AVAILABILITY</h2>
<p class="level0">Added in 7.18.0 <a name="RETURN"></a><h2 class="nroffsh">RETURN VALUE</h2>
<p class="level0">Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. <a name="SEE"></a><h2 class="nroffsh">SEE ALSO</h2>
<p class="level0"><a Class="manpage" href="./CURLOPT_SEEKDATA.html">CURLOPT_SEEKDATA</a> <a Class="manpage" href="./CURLOPT_IOCTLFUNCTION.html">CURLOPT_IOCTLFUNCTION</a> <span Class="manpage"> </span> <p class="roffit">
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